Costume backpack



FIG. 1 is a front, perspective view of a costume backpack showing my newdesign;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a top view therof; and,

FIG. 7 is a bottom view thereof.

The broken lines in the drawings illustrate environmental material thatforms no part of the claimed design.

The ornamental design for costume backpack, as shown and described.